1. Field of the Invention
The present invention relates to a photographic coupler and more particularly, it relates to a novel DIR coupler (Development Inhibitor Releasing Coupler) which is capable of releasing a development inhibitor upon reaction with an oxidation product of a developing agent and a silver halide photographic element containing same.
2. Description of the Prior Art
It is conventionally known to incorporate a compound which releases a development inhibitor upon development depending on the density of an image into a photographic light-sensitive material. The compound generally reacts with an oxidation product of a color developing agent and releases a development inhibitor. As a typical example, the so-called DIR coupler in which a group capable of exhibiting development inhibiting effects upon release from the active position is introduced in the active position of the coupler is known. The DIR coupler not only forms a dye but also releases a development inhibitor upon coupling with an oxidation product of a color developing agent. The compounds described in U.S. Pat. Nos. 3,227,554; 3,701,783; 3,615,506; 3,617,291, etc. and further improved compounds thereof such as the couplers in which a triazole ring or a diazole ring is bonded to the coupling position through the nitrogen atom of the 1-position in the triazole or diazole ring as described in Japanese Patent Application (OPI) No. 122335/1974 (Corresponding to U.S. Pat. No. 3,933,500) are known as DIR couplers. Using DIR couplers many effects can be obtained such as reduced graininess of image, improved sharpness of image due to edge effects, improved color reproduction due to interimage effects, controlling image tone, and the like. However, known DIR couplers do not provide such effects, in particular, improved sharpness of the image due to edge effects, and reduced graininess of the image, sufficiently. Therefore, it is desired to provide DIR couplers which provide these effects to a sufficiently large degree.